I would, as long as it is relevant to my blog posts, and is not some hate site or porn site. I also would as long as the content of people's comments were relevant.
Do you guys have any tips on good places to get free, quality backlinks? I want them mainly for SEO, but also so that people will click them and get to my site that way.
A forum signature link is manually made by the owner of a site (usually) and this is not natural. Google states that any unnatural link is blackhat SEO.